1. Field of the Invention
The present invention relates to methods and means for a data storage system which allows defects in the storage medium to be avoided; and, more particularly, to a data storage system, a storage medium, and a method of controlling the data storage system, which allows a defect (or defect area) extending over a plurality of consecutive defective blocks (or burst defective blocks) to be dealt with in a memory region of a reduced size.
2. Background of the Invention
With recent improvements in the recording density of a disk storage medium in a disk drive unit, an increasingly severe demand is imposed upon the disk storage medium. Concomitantly, it is becoming difficult to manufacture a perfect storage medium which is flawless throughout a record region, and thus such storage medium could be obtained only at an expensive price. In a disk drive unit, if data cannot be read/written from/into a physical sector (or block) normally, this sector is recognized as a defective sector and recorded on (or entered in) a defect map. To give an actual example, a disk drive unit having a capacity of 2 G bytes is provided with a memory which contains a storage region corresponding to 2000 defective sectors in the form of a defect map.
Such defective sectors are detected during the manufacture of a storage medium or during low level formatting. During logical formatting, logical block addresses (LBAs) are allocated to normal sectors which are not recorded on the defect map.
In regard to defective sectors which are produced during the use of the disk drive unit, since LBAs have already been respectively allocated to these defective sectors by the logical formatting, these defective sectors are recorded on the defect map and these LBAs are respectively allocated to substitute sectors.
By not allocating the LBAs to the defective sectors but allocating them to the substitute sectors, data can normally be read/written without errors from/into the storage medium containing a degree of defects. This permits a yield of the storage medium to be improved and its cost to be reduced.
The number of the defects each composed of (or including or extending over) a plurality of consecutive defective sectors increases as a recording density is improved. To give an actual example of the disk drive unit, a ratio of a number of the defects each composed of an isolated single defective sector (referred to as xe2x80x9csingle-sector defectxe2x80x9d) to a number of the defects each composed of a plurality of consecutive defective sectors (referred to as xe2x80x9cburst-sector defectxe2x80x9d) can be on the order of 3:7.
With regard to the burst-sector defects, if each of the defective sectors is recorded on the defect map, the redundancy is increased. Therefore, without reducing memory capacity, the number of the sectors which can be mapped out is not great.
To accommodate for this, there has been an attempt to record a defect in unit of a given number (a fixed length) of the sectors rather than record each of the defective sectors. This allows the burst-sector defects to be recorded on the defect map (referred to as xe2x80x9cfixed-length defect mapxe2x80x9d) efficiently, permitting the required memory capacity to be reduced.
However, if each defect is recorded in unit of a given number (a fixed length) of the sectors as mentioned above, it follows that a single-sector defects will also be recorded as a burst-sector defects having the fixed length, thus preventing an effective utilization of a record region on the storage medium. Specifically, after the logical formatting process, if each defect is treated as an unit of a plurality of defective sectors and substitute sectors on the memory are respectively allocated to the sectors in each defect, a lot of substitute sectors must be provided.
It is therefore an object of the present invention to provide a data storage system, a storage medium, and a method of controlling a data storage system, which allows a defect on a storage medium to be dealt with in a memory region of a reduced size.
A data storage system according to the present invention comprises, a storage medium having a record region which is blocked so as to include a plurality of blocks; a defective block recording means on which an address of a leading block of a defect area and length of the defect area are recorded; and a writing means for writing data into the plurality of blocks other than the block recorded on the defective block recording means.
Further, a storage medium according to the present invention comprises, a record region being blocked so as to include a plurality of blocks; and a defective block recording means on which an address of a leading block of a defect area and length of the defect area are recorded.
A method of controlling a data storage system according to the present invention comprises the steps of recording an address of a leading block of a defect area and length of the defect area, the defect area including at least one defective block; and writing data into the plurality of blocks other than the block recorded in the recording step.